Obtaining unaltered core samples



Nov. 20, 1962 H. c. BRIDWELL OBTAINING UNALTERED CORE SAMPLES 5 Sheets-Sheet 1 Filed Sept. 5, 1958 r O t n e m 3 O 4 l 6 2 w 3 8 p H 7 7 3 H Yum W i F 0 l m r. a B m u C If!! M O 'l C H 1962 H. c. BRIDWELL 3,064,742

OBTAINING UNALTERED CORE SAMPLES Filed Sept. 5, 1958 3 Sheets-Sheet 2 Harold C. Bridwell Inventor Byfikux Q' Attorney Nov. 20, 1962 H. c. BRIDWELL OBTAINING UNALTERED CORE SAMPLES 3 Sheets-Sheet 3 Filed Sept. 5, 1958 FIG. 6B Harold C. Bridwell lnvenior j'M 4 Aflgrney United States atent I @ilfice 3,064,742 Patented Nov. 20., 1962 3,064,742 OBTAINING UNALTERED CGRE SAMPLES Harold C. Bridwell, Tulsa, 91:151., assignor to Jersey Production Research Company, a corporation of Delaware Filed Se t. 5, 1953, Ser. No. 75%,277 Claims. (Cl. 175-226) The present invention concerns means for obtaining an uncontaminated core sample from a subterranean formation. It particularly relates to a method and apparatus for obtaining an uncontaminated core sample from a petroliferous formation at the bottom of a bore hole or well which penetrates the formation. The method and apparatus are particularly characterized by the fact that the core sample may be obtained without employing drilling mud, the presence of which has been found on occasion to seriously contaminate such samples. The method and apparatus are further particularly characterized by the fact (1) that the core sample may be continuously maintained under substantially ambient formation conditions, and (2) that it is sealed immediately after it is cut in order to prevent the loss of any fluids therefrom and to isolate it from the fluids that are present within a bore hole. The invention is especially directed to the coring of formations that are non-flowing and open to the atmosphere.

This application is a continuation-in-part of application Serial No. 512,452, filed June 1, 1955, in the name of the same inventor, and now abandoned.

A serious and important problem that confronts the petroleum producing industry at the present time is one of obtaining reliable samples of petroliferous formations that lie beneath the surface of the earth. The problem has become one of particular importance in view of the ever increasing use of secondary recovery methods for obtaining additional oil from subterranean oil reservoirs that have ceased primary production. It is essential, be fore initiating a secondary recovery procedure in any such reservoir, to have as much information as possible about the structure, the fluid content, the pore volume, the permeability, etc. of the reservoir. Such information is extremely valuable in determining whether the reservoir formation is susceptible of successful exploitation using secondary recovery techniques and just which technique should preferentially be utilized.

In line with the growing emphasis on secondary recovery programs, many petroleum producers are conducting extensive analyses of old reservoirs and fields that have lost their reservoir pressure and been abandoned. In an efiort to evaluate these old reservoirs and fields and in order to determine whether a secondary recovery procedure can be successfully applied to them, the producers are conducting extensive sampling programs. One sampling technique has been to drill and sample the bottoms or side walls of old wells that were originally producing wells associated with a reservoir or field. It has been determined, however, that the samples obtained by this technique are often not truly representative of the field or reservoir as a whole. Accordingly, it has become more and more the established practice to drill entirely new holes from the earths surface down to a petroliferous formation and to obtain samples of the formation directly from these new holes. Conventional drilling and coring methods such as rotary and cable tool have been employed for this purpose. In all of these types of drilling, however, it is necessary to use at least a small amount of drilling mud, water or other drilling fluid in the bottom of the hole in order to lubricate the bit and to dispose of the cuttings; and it is therefore conventional to have at least about 25 to 50 feet of water or other drilling fluid within a hole.

The presence of the drilling mud, water or other drilling liquid in a hole still constitutes an undesirable feature when sampling a reservoir of the type described above for the reason that the hydrostatic pressure and wetting efiects of even this small amount of liquid are considered to seriously interfere with the reliability of the samples that are obtained. It is accordingly an object of the present invention to provide an apparatus and method for obtaining reservoir core samples wherein the samples need not be subjected to a drilling liquid of any kind. It is a further object of the invention to provide means for coring a formation in such a manner that the core sample suffers very limited exposure to any material that could conceivably be a source of contamination. It is a particular object of the invention to provide means for isolating a core sample within the coring apparatus so that connate fluids are sealed within the sample. It is further a particuiar object of the invention to provide a coring method and apparatus wherein a core sample is sealed immediately after it is cut to protect it from contaminating substances such as the fiuids that are present within a borehole.

These objectives are realized in accordance with the present invention by the utilization of a core drill that possesses an outer barrel (otherwise sometimes referred to as an outer barrel or working barrel) including a coring bit, and an inner core barrel (otherwise sometimes referred to as an inner barrel or core-receiving barrel) which is at least partially filled with a core sealing agent and which is arranged to receive the core. As the core is cut by the core bit and enters the core-receiving or inner core barrel, the sealing agent is displaced from an inner portion of this barrel and is distributed over the outer surface of the core. The sealing agent acts to seal the pores of the core sample and thereby prevents fluids from escaping from the sample. The film of sealing agent additionally prevents contaminating substances from penetrating within the sample.

The coring action of the bit is abetted in accordance with the invention by passage of a stream of air or other suitable gasiform substance down the annular space between the inner and outer barrels to a point in the immediate vicinity of the cutting action. The air or other gasiform material is supplied from the earths surface down to the coring head by passage through suitable conduits and preferably through a string of drill pipe to which the core drill is attached.

The lower terminus of the air passageway is preferably directed away from the core sample in a manner such that the air serves the desired objectives of cooling the bit and removing cuttings from the hole without coming into actual contact with the core itself. Thus, air or other gasiform material is prevented from contaminating or altering the composition of the core.

As a core sample is cut by the present apparatus, the sample forces its way into the core-receiving barrel with the result that sealing agent is displaced from within this barrel and is deposited over the outer surface of the core sample. With reference to the sealing agent, it is additionally preferred that the agent be directed eventually in a stream that terminates at the bottom of the hole at a point laterally intermediate the core sample and the circulating air. Thus, the sealing agent serves the function of protecting the core sample from the action of any swirling air and seals the sample immediately as the sample is cut from the underlying formation.

Upon completion of the coring operation, the core sample is parted in a conventional manner and is held within the core-receiving barrel as by means of a conventional core catcher. Thereafter, the apparatus with its enclosed and sealed core sample may be withdrawn 3 to the earths surface for subsequent examination, observation, etc.

The invention may be better understood by reference to the attached figures wherein FIGURE 1 is a partially sectioned, vertical view of a coring head apparatus of this invention as it would be just prior to a coring operation;

FIGURE 2 is a partially sectioned and cutaway view of the core-receiving or inner barrel of the apparatus in FIGURE 1 as it would be immediately following a coring operation;

FIGURE 3 is a section taken along the lines III-4H of the apparatus in FIGURE 1;

FIGURE 4 is a partially sectioned, vertical view of another apparatus embodiment of the invention;

FIGURE 5 is a section view taken along the lines V-V of FIGURE 4;

FIGURE 6A and FIGURE 6B are upper and lower portions of the apparatus of FIGURE 4 as that apparatus is disposed after a core has been cut by the apparatus.

Turning to FIGURE 1, it will be observed that the coring assembly 5 illustrated therein includes an outer barrel 10, an inner or core-receiving barrel 11, a coring bit 14, a tool joint box 13, and a free piston member 19.

The outer barrel 10 terminates at its upper end in sealed relation with an adapter member 6 which in turn terminates in tool joint box 13. The joint box 13 is provided with threads or other suitable means for securing it to the lower end of a string of drill pipe not shown.

The lower end of the outer barrel 10 is threaded or otherwise secured to the coring head 14 as by means of the illustrated threaded arrangement or any other suitable and conventional system for connecting such members. The coring head 14 may be provided with cutting teeth 15 as illustrated or which may be furnished with suitable cutting material such as diamond particles and the like.

The inner or core-receiving barrel 11 is disposed within the outer barrel 10 in a manner so as to define an annular passageway 12 laterally intermediate the two barrels. Passageway 12 extends the length of the two barrels and afiords a continuous fluid path from the tubing string above the coring apparatus down to the discharge jets 16 that are positioned within the coring bit proper. Sealing means 29 efiecting a fluid-tight seal between coring head 14 and the lower extension of inner barrel 11 prevents drilling fluid from flowing directly into contact with a core entering within the inner barrel.

The inner barrel 11 is blanked off at its upper end as by means of a solid plug member 18 which may be threaded or otherwise secured to the upper end of this barrel member. As illustrated, the upper end of inner barrel 11 is also fixed in its relationship to the outer barrel 10 as by means of an annular-type adapter 23. In the FIGURE the adapter 23 is permanently secured to the inner wall surface of the outer barrel 10 as by means of a welded connection, a threaded connection or any other suitable means. The inner surface of the adapter 23 is secured to the inner barrel 11 as by means of a conventional threaded joint. The adapter is furthermore provided with one or more passageways 24 to provide a flowpath for the air or other gasiform drilling fluid to flow from the tubing string into the annular passageway 12 between the two barrel members. The nature of the passageways 24 is more clearly illustrated and understood by reference to FIGURE 3.

Plug member 18 is preferably of a character such that it may be periodically removed as desired from the inner barrel 11. If permanently secured to the inner barrel, however, plug member 18 may be provided with a suitable valve arrangement for venting the interior portion of the core barrel when such is desirable. As will be more apparent later in this description, venting of the core-receiving barrel is particularly desirable when the interior of the barrel is being loaded with a sealing agent.

Positioned within the lower end of barrel 11 is a free piston member 19 which is of a character such that it may slide along the inner surface of the barrel. The outer wall surface of the piston member and the inner wall surface of barrel 11 are preferably finished surfaces such that relatively free but fluid-tight movement is provided between these two members. In order to insure a fluid-tight relationship between the members, suitable O-rings 20, piston rings, or other sealing arrangements are provided.

Disposed within piston member 19 and extending the length thereof is a passageway 21 which provides a flow path for fluid to enter or leave the portion of the core barrel immediately above the piston member 19. It will be appreciated that an enclosed chamber 25 is defined within barrel 11 by the inner wall surface of the barrel in combination with the plug member 18 and the upper surface of the piston member 19. Access to this chamber from a point outside the coring apparatus proper is provided by the passageway 21.

Disposed within the passageway 21 at a point vertically intermediate its upper and lower extremities is a check valve 26 which is spring loaded such that fluids can be forced from a point within the chamber 25 to a point beyond the piston 19 but not in the reverse direction. Once beyond the check valve 26, any fluid flowing from chamber 25 is directed preferably toward the outer wall surface of the piston 19 and downwardly toward the bottom surface of the piston. An inclined passageway such .as the passageway 30 illustrated in FIGURE 1 is suitable for the purposes of the invention. It will be appreciated, of course, that a plurality of such passageways may be employed for the same general purpose, the purpose being to distribute the fluid which flows downwardly through these passageways substantially evenly over the outer surface of a core positioned immediately below the cylinder 19. V

A second passageway 31 immediately below valve 26 is provided for the purpose of inserting the valve and spring. Ordinarily, this passageway is plugged as by means of a threaded plug member 32.

It will be noted in FIGURE 1 that the inner barrel 11 is provided with a small fitting 33 in its side wall at a point near the upper end of the barrel. This fitting serves the purpose of an opening through which to inject the sealing agent into the inner barrel.

Having discussed the various structural features of the apparatus of this invention, attention is now directed to a brief description of the manner in which the apparatus is employed. At the outset of this description, it is well to note that the apparatus is intended primarily for use in conjection with a conventional string of drill pipe. Thus, the assembly illustrated in FIGURE 1 is secured to the lower end of a string of drill pipe as by means of the threaded tool joint box 13. With the coring assembly disposed in this manner, the drill pipe and the attached assembly are then lowered to the formation which is to be cored. As pointed out earlier, the apparatus is primarily adapted for obtaining core samples from formations that are non-flowing and that are under substantially atmospheric pressure. With this in mind, the apparatus is lowered through a bore hole to the formation to be cored and its operation is commenced by passing a gasiform drilling fluid from the earths surface down through the drill string and thence through the annular passageway 23 and 12 to the jet passageway 16.

At this point the apparatus is revolved as by means of a conventional rotary table and drilling apparatus, and the cutting teeth 15 of .the bit 14-are driven into the underlying formation. Cuttings formed by the cutting teeth are carried to the surface of the earth or to a cutting basket conveniently disposed above the drilling apparatus by means of the upflowing gas that issues from the jet nozzles 16. The gas also serves the additional function of cooling the bit as it progresses in its cutting action.

As a result of the cutting action, a core sample 34 such as is illustrated in FIGURE 2 is driven up within the inner or core-receiving barrel 11 and drives the piston 19 ahead of it. As the piston 19 rises within the barrel 11, it exerts a pressure upon the liquid sealing agent which is disposed within the barrel 11 with the result that the sealing agent flows down through passageway 21 and pushes valve 26 from its seat.

The sealing fluid then flows through the passageway 30 and discharges into the annular space 22 which exists between the outer wall surface of the piston 19 and the inner wall surface of the barrel 11. From this point the sealing agent is extruded down and around the core 34 until it discharges from the lower end of the barrel 11.

Since the inner barrel 11 is secured firmly to the outer barrel 10, the inner barrel rotates with the outer barrel; and both barrels rotate with respect to the core 34 so long as the core is not separated from the underlying formation. This relative movement between the inner barrel 11 and the core serves to aid the distribution of the sealing agent over the surface of the core. It will be noted, however, that eflicient distribution of the sealing agent is achieved whether or not rotational movement between the inner barrel 11 and the core is continuously maintained.

As the core 34 enters the inner barrel 11 it engages the core catcher 27 which prevents the core from slipping out of the core barrel at any point during or subsequent to the coring operation. Thus, when the coring operation has been completed and a suflicient core provided within the inner barrel 11, rotation of the apparatus is ceased and the apparatus is withdrawn to the earths surface. Y

At this point in the operation, the inner barrel of the apparatus is substantially in the condition illustrated in FIGURE 2. There it may be seen that the piston 19 has been driven completely within the inner barrel and is resting upon the top of the core sample 34. Furthermore, the sealing agent originally provided within the inner barrel has been forced through the passageway 21 and thence distributed over the outer surface of the core.

At this point it is well to note that a number of different gasiform fluids may be employed in utilizing the principles of this invention. In general, it is necessary that the fluid be gasiform under the conditions that prevail .at the bottom of a bore hole and that it be substantially chemically inert toward the apparatus as well as toward the core. Suitable gases therefore include the chemically inert gases such as nitrogen, neon, helium, etc. as well as other readily available gases such as air, dry flue gas, steam, and the like. Other suitable gases include the exhaust gases from internal combustion engines such as diesel engines, gasoline engines, gas turbines, etc.

In view of the ready availability of air it is generally preferred to employthis gas as the drilling fluid in the process of this invention.

Regardless of the gas that is selected for use in the invention, however, it is necessary that the flow rate of the gas be suflicient to remove the cuttings that are formed by the apparatus from the vicinity of the cutting bit. Thus, in a conventional bore hole it is desired that gas flow rates be employed that are sufficient to provide a gas velocity in the annular space between the apparatus and the wall of the bore hole of the order of 100 to 150 ft. per second. Velocities of this order of magnitude not only remove cuttings from the bore hole but also very effectively cool the coring bit.

Insofar as the choice of sealing agent is concerned, it is necessary that this material flow readily under the ambient conditions that prevail during a coring operation and that it be substantially chemically inert toward the apparatus as well as toward the core sample. The sealing agent furthermore should be non-wetting in that it not have a tendency to bond to or penetrate the core sample. It is additionally preferred that the agent possess lubricating qualities so as to reduce the amount of friction that customarily exists between the core and the core-receiving barrel. It is further preferred that the agent be substantially chemically inert toward the gasiform drilling fluid as well as toward water and the hydrocarbons that are present within the core sample.

In addition to the above characteristics, it is desirable that the sealing agent be of a character to form a film over the surface of a core sample which effectually seals off the surface of the sample. In this connection the agent should preferably be a good lubricant with a specific gravity of one or greater and a viscosity of 1000 centistokes or more.

Suitable sealing agents for the purposes of the invention may be selected from a wide variety of materials. Thus, it is contemplated that suitable agents include a number of well known polymers, thermoplastic materials, thermosetting resins, low melting alloys, low melting metals and the like.

Particularly suitable sealing agents are the polymeric silicones that possess a viscosity in excess of 1000 centistokes. Also particularly suitable are thermoplastics such as polyvinyl chloride and polyesters including the reaction products of (l) adipic acid and hexamethylene diamine, (2) maleic anhydride and ethylene glycol, (3) phthallic anhydride and ethylene glycol.

Especially effective sealing agents are considered to be thermosetting synthetics such as the condensation products of (1) cresol and formaldehyde, (2) furfural, (3) adipic acid and glycerol. With respect to these and other thermosetting resins, it will be noted that it is contemplated that a core cut with one of these agents be maintained within a bore hole for a time sufficient for the resin to set before being removed from the hole. Reaction times and conditions suitable for this purpose are well known in the art, and a detailed discussion of such factors is not considered to be necessary here. It will further be noted that it may be desirable in connection with thermosetting agents to employ core-receiving barrels that are readily severable and disposable.

Low melting alloys and metals that may be employed as sealing agents include lead, mercury, bismuth and tin. The eutectic of lead and bismuth is particularly contemplated.

At this point it will be noted that the invention is not intended to be limited in its scope to the specific embodiments and examples presented hereinbefore but rather by the claims that follow. For example, it is contemplated that the core-receiving barrel may utilize an inner barrel member and an outer barrel member that are separated by an annular space. The sealing agent may then be arranged to be extruded between the outer member of the core barrel and the outer or Working barrel of the entire coring assembly. In this manner, the sealing agent effectively seals off the core from the fluids within the bore hole without itself coming into contact with the core.

It is further contemplated that the invention may be practised with the utilization of other conventional drilling, coring and sampling apparatus. For example, it is particularly contemplated that the invention may be employed in conjunction with a pressure core barrel such as is described in United States Patent No. 2,216,962.

To illustrate how this invention may incorporate features such as a double-walled core-receiving barrel as Well as a pressure core barrel, attention is next directed to the remaining figures in the drawing. It will be noted in examining these figures that components or parts shown in these figures which have counterparts in FIG- URES l-3 are identified by common legends.

Referring, then, to FIGURE 4, the apparatus shown in this figure includes a tool joint box 13, an outer or working barrel 10, coring bit head 14, jets l6, and a piston 19. Piston 19, it will be noted, varies somewhat from the piston in FIGURE 1 in that it lacks any central fluid passageway or check valve.

Other components shown in FIGURE 4 include an 7 inner barrel assembly which comprises a core-receiving barrel 51 and an intermediate barrel 52. Both of these barrels are supported, directly or indirectly, from rod 53. Thus, the upper end of barrel 52 is threaded directly into the lower end of the rod; and barrel 51 is suspended from barrel 52 by means of a swivel bearing 54.

The upper end of rod 53 terminates in a head 55. A down-turned flange or shoulder 56 is positioned at an intermediate point along the rod 53. One or more fluid passageways 57 are provided within flange 56.

The barrel 51 has a plurality of ports or passageways 58 near its upper end. It is also provided with a core catcher 59 at its lower end, and it is rigidly secured to piston 19 (prior to coring) by means of a shear pin 60. Piston rings, O-rings, or the like 61 are positioned between piston 19 and the inner wall surface of barrel 51 to provide a sliding fluid-tight relationship therebetween. A similar ring or seal 62 is provided between the lower outer surface of barrel 52 and the coring head 14.

Positioned around and partially encasing barrel 52 is a sleeve 63, which has a flange 64 at its upper end that is slidable relative to rod 53. 'As will be more apparent from FIGURES and 6B, the lower end of sleeve 63 terminates in bifurcated extensions 90 which rest upon shoulder 72. Each extension 90'has a pivot '65 upon which a spherical or ball-type valve 66 is supported. Valve 66 has a port 67, which when the valve is open enables the barrels 51 and 52 to move through the valve. Valve seat 68 for valve 66 is located at the lower end of the main body of the sleeve 63.

Portions of the surface of the ball valve 66is geared as at 69 so as to engage racks 70 in member 71. Member 71 is, in efiect, a segment of a cylinder which is held rigidly between the shoulder 72 of the coring head 14 and the lower end of the barrel 10. A rack 70 along each side of member 71 engages a separate geared portion 69.

The upper end of barrel is connected to a collar 75 which is slidable relative to box 13. Cooperating flanges on the collar 75 in the lower extension of box 13 limit longitudinal movement between these two members. The lower end of box member 13 and barrel 10 are splined or keyed so as to be rotatable with one another.

The lower portion of box 13 is also provided with a dog 76 which is pivoted at 91 and spring-loaded so as to normally urge the dog radially inward toward the rod 53. A shoulder 77 on the lower end of head 55 enables the rod to rest upon the dog 76 when the rod has been raised relative to the dog a suflicient distance.

The under surface of the flange 64 is provided with a circular knife edge 78 which, as will become clear in the following description, on occasion engages circular seat 79 on the upper end of barrel 52.

Having described very briefly the various parts of the apparatus shown in FIGURES 4, 5, and 6, attention is now directed to the manner in which this apparatus is made to operate. The discussion of its operation will further assist in explaining its construction, since certain critical dimensions of the apparatus will be considered and explained.

Referring, then, to FIGURE 4, the apparatus is-depicted as it appears when lowered within a borehole for the purposes of taking a core. Valve 66 is open, and the barrels 51 and 52 extend through the valve and rest .upon the ledge 80. The piston is rigidly secured at the entrance to barrel 51 by means of shear pin 60. The lower end of the piston extends below bit head 14 a distance which is greater than the distance between the shoulder 77 of the head 55 and the surface 81 of the dog 76. The distance the piston extends beyond the bit head 14 is also greater than the distance the flange 56 on rod 53 must travel upward relative to box member 13 so as to engage the shoulder 82 at the lower end thereof.

The interior of barrel 51 is filled with a core-sealing fluid of a type described hereinbefore. As shown in the figure, the fluid extends up to the level of the ports 58. In fact, the fluid may also fill these ports as well as the annular space between the barrels 51 and 52. Generally speaking, seating of these barrels upon the ledge 80' will provide a suflicient seal to retain the fluid within the annular space between the barrels as the assembly is lowered into a coring position.

When the apparatus of FIGURE 4 reaches the bottom of a borehole, and when the weight of the apparatus and the drill string above it is transmitted to the piston 19, the drill string and outer barrel 10 move downward relative to the piston. Piston 19, therefore, effectively enters within the outer barrel 10; and the barrels 51 and 52 are lifted from the ledge 80. This relative movement between barrels 51 and 52 and the outer barrel 10 continues until shoulder 56 strikes against shoulder 82 Meanwhile, the spring-loaded dog 76 will have moved inward; and surface 81 will have engaged shoulder 77 as shown in FIGURE 6A. 'When flange 56 and shoulder 82 engage one another, shear pin breaks; and piston 19 is now free to move relative to barrel 51. 7

With the apparatus of FIGURE 4 now in a coring disposition, bit head 14 is caused to cut a core in a conventional manner as by rotating box 13 through the drill string to which it is attached. The splines or keying arrangement between box 13 and the outer barrel 10 enables these members to rotate together. Drilling fluid is passed down through the drill string and the box member 13, then through ports 57 and the annular passageway 83 to the jets 16 in the bit head 14. The fluid then flows upward within the borehole between the drilling apparatus and the wall of the hole to the surface of the earth.

As coring continues, the barrels 10, 51, and 52 all move downward relative to the piston 19. The piston and the core upon which it rests enter Within the barrel 51 and thereby cause fluid to be displaced from the barrel through the ports 58. The displaced fluid moves down through the annular space between the barrels 51 and 52, where it is finally extruded around the surface of the piston 19 and the core below it. The core'is therefore continuously coated with the material and also protected from the drilling fluid which flows through the bit head 14. e

When coring has been completed, the core may be parted in a conventional manner as by decreasing the load on the bit and rotating it at an increased rate.

With the core parted, the core catcher 59 serves to hold the core within the barrel 51 as shown in FIGURE 6B. At this point, the drill string and the box member 13 are lifted, whereupon the ledge 84 engages the-lower end of the collar 75. Prior to the time, however, that ledge 84 strikes collar 75, dog 76fastened to member 13 as it is-lifts rod 53 and barrels 51 and 52 up through valve 66 and into the sleeve 63. p

The distance ledge 84 must move before engaging collar 75 must always be greater than the distance that seat 79 must move to engage knife edge 78 together with the distance that gears 69 must roll along racks in order to close valve 66. Thus, as box member 13 is lifted upward relative to barrel 10, it first lifts rod 53. through dog 76 and head 55 until seat 79 is engaged firmly against knife edge 78. At this point, further upward movement of the box member and rod 53 causes sleeve 63 also to be moved upward within barrel 10. Since member 71 is rigidly held between barrel 10 and bit head 14, this means that sleeve 63 will move upward relative to the member 71. Gears 69 will therefore roll along racks 70, and valve 66 will then be rotated into the closed position shown in FIGURE 6B. Upon referring to that figure, it will be noted that passageway 67 is now laterally disposed and seat 68 at the lower end of the sleeve 63 is now closed or sealed.

As mentioned above, by properly spacing the various elements of the apparatus in FIGURE 4, ledge 84 is caused not to engage collar 75 until the barrels 51 and 52 are completely within sleeve 63 and until valve 66 has been closed. At this point, further upward movement of member 13 causes it to engage collar 75 and to thereby raise the barrel and its bit head 14. The entire apparatus may then be removed from the borehole and the core recovered from the barrel.

What is claimed is:

1. In a coring apparatus arranged to be positioned at the lower end of a drill string including an outer barrel member, a coring bitcarried by the outer barrel member, and a core-receiving barrel disposed within said outer barrel member .adapted to receive a core the improvement which comprises a freely movable piston disposed within said core-receiving barrel and adapted to move upwardly .within thecore-receiving barrel upon the entry of a core, a fluid core sealing agent disposed within said core-receiving barrel above said piston, and conduit means arranged to conduct said sealing agent upon upward movement of said piston in the form of a substantially continuous film to the annular space between the core and the inner wall surface of the core-receiving barrel below the piston.

2. In acoring apparatus arranged to be operated at the lower end of a string of drill pipe and including an outer barrel, a coring bit carried by the outer barrel and conduits suitable for conducting a drilling fluid from the drill string to the coring bit, the improvement which comprises in combination a core barrel assembly disposed within said outer barrel, said assembly consisting of two concentrically disposed and spaced barrel members, the inner barrel member arranged to receive a core cut by said coring bit, a piston disposed within said inner barrel member and arranged to be moved upwardly by the entry of said core, and conduit means separate from said conduits connecting the portion of the inner barrel member lying above the piston with the annular space between said inner barrel member and said outer barrel member, said conduit means being adapted to convey fluid from within the portion of the inner barrel member above the piston in response to upward movement of said piston, the lower end of said barrel members being arranged to discharge said fluid from said annular space around the outer surface of said core.

3. An apparatus as defined in claim 2 including means to eflect a fluid tight seal between the lower end of the outer barrel member and the outer barrel.

4. In an apparatus for coring the bottom of a borehole and including an outer barrel, a core-receiving inner barrel disposed within said outer barrel, a coring bit carried by the outer barrel, and first conduit means between said inner and outer barrels for the passage of drilling fluid, the improvement which comprises: a piston fitted within and movable along said inner barrel, the inward-facing end of said piston defining together with said inner barrel a chamber adapted to contain a fluid core-sealing agent, and second conduit means distinct from said first conduit means, one end of said second conduit means communicating with said chamber above said piston and arranged to receive fluid therefrom upon movement of said piston further into said inner barrel, the opposite end of said second conduit means arranged to discharge fluid received from said chamber against the surface of a core entering within said core-receiving barrel.

'5. In a coring apparatus including a bit and a corereceiving barrel mounted adjacent thereto and adapted to receive a core as it is cut by the bit, the improvement which comprises a piston disposed within said core receiving barrel and movable along the length thereof, the inward-facing end of said piston together with the interior surface of said core-receiving barrel defining a chamber adapted to retain fluid, a fluid core-sealing agent within said chamber, a laterally confined conduit terminating at one end within said chamber inward of said piston and arranged to receive said agent from within said chamber upon movement of said piston further into said core-receiving barrel, said conduit terminating at its other end in a manner to discharge said agent around the surface of a core entering within said core-receiving barrel.

6. In a coring apparatus which includes an outer barrel member, a coring bit carried at the lower end of said outer barrel, a core-receiving inner barrel disposed within said outer barrel, and first conduit means of a character to discharge drilling fluid through said apparatus to the vicinity of said coring bit, the improvement which comprises: a piston fitted within and movable along said inner barrel, the upward surface .of said pistontogether with the inner surface of said inner barrel above said piston defining a chamber adapted to contain fluid, s ec ond conduit means distinct from said first conduit means, said second conduit means at one end communicating with and arranged to receive fluid from said chamber upon upward movement of said piston within said inner barrel, said second conduit means at its other end arranged to discharge fluid received from said chamber against the surface of a core received by said inner barrel, and fluidtight sealing means interposed between the entrance to said inner barrel and the discharge end of said first conduit means.

7. In a rotary coring apparatus including an outer barrel, a coring bit carried by the lower end of said outer barrel, an inner core-receiving barrel mounted within said outer barrel, and fluid passageway means between said barrels for conveying drilling fluid down to said bit, the improvement which comprises a piston movably disposed within said core-receiving barrel and defining therewith an enclosed spaced above said piston of a character to contain fluid, conduit means separate from said fluid passageway means connecting said enclosed space with the annular space defined between a core within the core-receiving barrel and the inner Wall surface of the core-receiving barrel, said conduit means adapted to provide for flow of fluid from within said enclosed space upon upward movement of said piston within said core-receiving barrel.

8. In a rotary coring apparatus arranged to be positioned at the lower end of a drill string and including an outer barrel, a coring bit carried by the lower end of said outer barrel, a core-receiving barrel disposed within said outer barrel and adapted to receive a core cut by said bit, and a conduit between said core-receiving barrel and said outer barrel arranged to receive drilling fluid from said drill string and to discharge said fluid in the vicinity of said coring bit, the improvement which comprises a piston fitted Within said core-receiving barrel and adapted to move upwardly upon the entry of a core therein, a fluid core-sealing agent disposed Within said core-receiving barrel above said piston, and conduit means distinct from said conduit arranged to receive said sealing agent from said core-receiving barrel upon upward movement of said piston and to discharge said agent against the surface of a core entering within said core-receiving barrel.

9. In a rotary coring apparatus including an outer barrel adapted at its upper end to be connected to the lower end of a drill string, a coring bit carried by the lower end of said outer barrel, and a core-receiving barrel disposed Within and supported by said outer barrel, the improvement which comprises a conduit between said outer barrel and said core-receiving barrel adapted to transmit drilling fluid from within said drill string to the vicinity of said coring bit, the lower end of said conduit being directed away from the entrance to said core-receiving barrel, a piston fitted and longitudinally movable within said core-receiving barrel and defining therewith and above said piston a chamber of a character to contain fluid, conduit means adapted at one end to receive fluid from within said space and at its other end to discharge fluid against the surface of a core received by said core-receiving barrel.

r 10. ,A rotary coring apparatus which comprises an outer barrel adapted at its upper end to be connected to the lower end ofia drill-string, a coring bit adapted to be connected'to the lower end of said outer barrel, a core barrel assembly disposed within said outer barrel, said assembly comprising two concentrically disposed and spaced barrel members, the inner barrel member arranged to receive a core cut by said coring bit, a piston disposed within said inner barrel member and arranged to be moved upwardly by the entry of said core, conduits between the outer barrel member and said outer barrel arranged to conduct drilling fluid from said drill string to said coring bit, eonduit means separate from said conduits, one end of said conduit means arranged to receive fluid from the portion of said inner barrel member lying above said piston, the other end of said conduit means arranged to discharge 12 fluid against the outersurface of a core entering within said inner barrel member, and valve means operable to close off the, lower end of said inner barrel member.

References Citedin the fileof this patent UNITED STATES PATENTS 1,952,170 Humasonet a1 Mar. 27, 1934 2,264,449 Mounce 'Dec.' 2, .1941 72,343,805 j Sewell Mar. 7, 1944 2,347,726 Auld et a1 May 2, 1944 2,364,088 Miller et a1 Dec. 5, 1944. 2,541,785 'Smith Feb. 13, 1951 2,587,231 Schierding Feb. 26, 1952 2,703,697 Walker Mar. 8, 1955 2,862,691 Cochran Dec. 2, 1958' 2,880,969 Williams Apr. 7, 1959 

